281 
FXUS63 KFSD 260948
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
348 AM CST SAT JAN 26 2013

.DISCUSSION.../ISSUED AT 348 AM CST/

SURFACE RIDGE AXIS LOCATED THROUGH MINNESOTA AND IOWA VERY EARLY 
THIS MORNING WILL PUSH OFF TO THE EAST TODAY...WITH A RETURNING 
SOUTHERLY FLOW ON THE BACKSIDE OF THE HIGH BRINGING WARMING 
TEMPERATURES TO THE AREA. 925 MB TEMPERATURES PROGGED TO AVERAGE A 
GOOD 10 DEGREES C WARMER THAN YESTERDAY...THOUGH WITH A STRONG 
INVERSION OVER THE AREA WILL PROBABLY NOT MIX THAT HIGH...BUT HIGHS 
WILL RESPOND TO THE WARMING THERMAL PROFILES AND TOP OUT MID 20S 
IN OUR FAR NORTHEAST TO AS WARM AS THE MID 40S OVER OUR FAR SOUTH 
CENTRAL SOUTH DAKOTA ZONES. WILL BE A PARTLY TO MOSTLY SUNNY DAY 
WITH JUST A FEW HIGH TO MID CLOUDS STREAMING AROUND THE LONGWAVE 
UPPER LEVEL RIDGE SITTING OVER THE REGION. WILL BE A BIT BREEZY THIS 
AFTERNOON WITH A TIGHTENING GRADIENT AND WINDS AROUND 20 TO 25 KTS 
AT THE TOP OF THE MIXED LAYER.

A SURFACE WARM FRONT LIFTS UP ACROSS THE AREA TONIGHT...AS AN UPPER 
LEVEL SHORTWAVE BEGINS TO TRACK OUT OF NORTHEASTERN COLORADO. WHILE 
MUCH OF THE NIGHT WILL BE DRY...DO EXPECT PRECIPITATION TO BEGIN TO 
DEVELOP LATER AT NIGHT IN OUR SOUTHEAST...BECOMING LIKELY BY SUNDAY 
MORNING AS OPTIMAL SYNOPTIC LIFT AS EVIDENCED BY 500 MB DIV Q AND 
BEST MIDLEVEL ISENTROPIC LIFT INCREASE ACROSS NORTHWEST IOWA DURING 
THE EARLY PART OF THE DAY. WHILE TEMPERATURES ALOFT WILL BE WELL 
ABOVE 0 C BY THAT TIME...SURFACE TEMPS STILL LOOK TO BE RIGHT AROUND 
30 DEGREES OVER THAT AREA BEFORE 15Z...THEN SLOWLY WARMING AFTER 
THAT. IN LIGHT OF THAT...WENT AHEAD AND ISSUED A FREEZING RAIN 
ADVISORY IN OUR SOUTHEASTERN ZONES FROM 11Z TO 17Z WHEN THAT AREA IS 
MOST LIKELY TO SEE SOME ICING. DO NOT ANTICIPATE MAJOR ICING AT THIS 
TIME...WITH ANY ICE ACCUMULATIONS GENERALLY IN THE RANGE OF TWO TO 
FOUR HUNDREDTHS THROUGH THE SIOUX CITY TO SPENCER CORRIDOR...THEN 
RAPIDLY TAPERING DOWN BACK TO THE NORTH AND WEST. BY AFTERNOON 
EXPECT TEMPERATURES TO RISE INTO THE MID AND UPPER 30S...SO WOULD 
MAINLY SEE PLAIN RAIN BY THAT TIME.

FORCING QUICKLY PULLS AWAY ON SUNDAY EVENING WITH ANY LINGERING 
PRECIPITATION IN OUR FAR EAST WINDING DOWN. MODELS HINTING AT 
POSSIBLE STRATUS ON SUNDAY NIGHT...AND IF IT STAYS CLOUDY THROUGH 
THE NIGHT LOWS MAY BE A LITTLE WARMER THAN PRESENTLY FORECASTED WITH 
RELATIVELY WARM THERMAL PROFILES REMAINING OVER THE AREA. PRESENTLY 
HAVE LOWS AROUND 20 IN THE NORTHWEST TO AROUND 30 IN OUR FAR 
NORTHWESTERN IOWA ZONES.

MODELS CONTINUE TO BE ALL OVER THE PLACE WITH THE MONDAY/MONDAY 
NIGHT SYSTEM...SO STUCK CLOSE TO A CONSENSUS BLEND WITH REGARD TO 
POPS THROUGH THE PERIOD. MODEL THERMAL FIELDS STILL FAIRLY WARM FOR 
MOST OF MONDAY...SO PRECIPITATION TYPE WOULD AGAIN BE IN THE FORM OF 
RAIN/FREEZING RAIN...DEPENDENT ON SURFACE 
TEMPERATURES...TRANSITIONING TO SNOW FROM THE WEST LATE IN THE DAY 
AND INTO THE EVENING AS 850 MB TEMPERATURES SLIDE UNDER 0 C. DO 
THINK THAT SOME PORTION OF OUR AREA WILL HAVE A PRETTY GOOD SHOT OF 
SNOW ON MONDAY NIGHT...WITH ALL MODELS POINTING TOWARD THE 
DEVELOPMENT OF STRONG MIDLEVEL FRONTOGENESIS ACROSS THE 
AREA...THOUGH DIFFERING ON THE EXACT PLACEMENT OF THIS FEATURE. WILL 
BE SOMETHING TO WATCH HOWEVER. HIGHS ON MONDAY LOOK TO BE IN THE MID 30S 
NORTH TO UPPER 30S SOUTH. LOWS ON MONDAY NIGHT WILL BE MAINLY IN THE 
20S.  /JM

OPEN UPPER WAVE MOVES ACROSS THE MIDDLE PORTION OF THE U.S. TUESDAY 
AND TUESDAY NIGHT. BOTH THE GFS AND ECMWF ARE IN PRETTY GOOD 
AGREEMENT WITH THE LARGE SCALE OF THIS SYSTEM...WHICH KEEPS OUR 
FORECAST AREA IN THE NORTHERN JET STREAM AND GENERALLY CUT OFF FROM 
THE DEEPER MOISTURE. THEREFORE PRECIPITATION CHANCES ARE LEFT IN THE 
CHANCE CATEGORY FOR MUCH OF OUR FORECAST AREA ON TUESDAY...WITH 
SLIGHT CHANCES TUESDAY NIGHT. KEPT THE TYPE OF PRECIPITATION AS 
SNOW. EVEN THOUGH SOME OF THE 925MB TEMPERATURES ARE ON THE POSITIVE 
SIDE OF ZERO CELSIUS...TEMPERATURES FURTHER UPSTAIRS ARE BELOW ZERO. 
FURTHERMORE...A NORTHWEST SURFACE WIND SHOULD GIVE SOME EVAPORATIVE 
COOLING AFFECT. THE REST OF THE EXTENDED LOOKS DRY AT THIS TIME...
ASIDE FROM MAYBE SOME FLURRIES FRIDAY NIGHT JUST BEYOND THIS CURRENT 
EXTENDED TIME FRAME. THE BIGGER STORY WILL BE TEMPERATURES. ONE COLD 
SURGE MOVES SOUTHWARD TUESDAY NIGHT...FOLLOWED BY A STRONGER SURGE 
OF COLD AIR WEDNESDAY NIGHT AND THURSDAY. BOTH THE DETERMINISTIC GFS 
AND ECMWF ARE IN GOOD AGREEMENT WITH THE PLACEMENT AND TIMING OF 
THESE SURGES. THEREFORE INCREASED THE WIND SPEEDS IN THE WEDNESDAY 
NIGHT AND THURSDAY TIME FRAMES FROM THE ALL BLEND SPEEDS AND BLENDED 
IN SOME RAW GFS AND ECMWF OUTPUT. TEMPERATURES WILL THEREFORE BE 
COLD ONCE AGAIN FROM WEDNESDAY ONWARD.  /MJF

&&

.AVIATION.../FOR THE 06Z TAF ISSUANCE/
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. WINDS 10 KT OR LESS 
OVERNIGHT WILL GRADUALLY TURN SOUTH SOUTHEAST BY 15Z AND INCREASE TO 
10 TO 15 KT WITH GUSTS TO 20 KT BY 18Z. STRONGEST WINDS WILL BE EAST 
OF THE JAMES RIVER.

&&


.FSD WATCHES/WARNINGS/ADVISORIES...
IA...FREEZING RAIN ADVISORY FROM 5 AM TO 11 AM CST SUNDAY FOR 
     IAZ012>014-020>022-031-032.

MN...NONE.
NE...FREEZING RAIN ADVISORY FROM 5 AM TO 11 AM CST SUNDAY FOR NEZ013-
     014.

SD...FREEZING RAIN ADVISORY FROM 5 AM TO 11 AM CST SUNDAY FOR SDZ071.

&&

$$